Fire retardant and heat resistant yarns and fabrics treated for increased strength and liquid shedding

ABSTRACT

Fire retardant and heat resistant yarns and fabrics include an inner core comprised of oxidized polyacrylonitrile encapsulated by an outer shell comprised of a liquid-resistant and strengthening polymer material. The liquid-resistant and strengthening polymer material includes one or more types of cured silicone polymer resin. A fluorchemical may be at least partially impregnated into the inner core prior to applying the liquid-resistant and strengthening polymer material in order to further enhance the liquid shedding properties of the yarns or fabric. Because the silicone polymer resin only encapsulates the yarn, but does not form a continuous coating over the whole fabric, the treated fabric is still able to breath through pores and spaces between individual yarn strands that make up the fabric. The liquid-resistant and strengthening polymer material increases the strength, abrasion resistance, durability and liquid and gel shedding capability of the fire retardant heat resistant yarn or fabric.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. § 119 of U.S.provisional application Ser. No. 60/786,853, filed Mar. 29, 2006, thedisclosure of which is incorporated herein in its entirety.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention is in the field of fire retardant and heatresistant yarns and fabrics. More particularly, the present invention isin the field of fire retardant and heat resistant yarns comprised ofoxidized polyacrylonitrile fibers and encapsulated with aliquid-shedding and strengthening polymer, as well as fabrics andarticles of manufacture made therewith.

2. The Relevant Technology

Fire retardant clothing is widely used to protect persons who areexposed to fire, particularly suddenly occurring and fast burningconflagrations. These include persons in diverse fields, such as racecar drivers, military personnel, and fire fighters, each of which may beexposed to deadly fires and extremely dangerous incendiary conditions.For such persons, the primary line of defense against severe burns andeven death is the protective clothing worn over some or all of the body.

Even though fire retardant clothing presently exists, such clothing isnot always adequate to reliably offset the risk of severe burns, or evendeath. This is particularly true in the case where a person is not onlyexposed to flame or high heat but splashed with a flammable hydrocarbonliquid (e.g, gasoline). This could occur, for example, in the case of avehicle crash or by deliberate sabotage (e.g., a Molotov cocktail orother incendiary device hurled at a policeman or military personnel).

A wide variety of different fibers and fibrous blends have been used inthe manufacture of fire and heat resistant fabrics. Fire retardance,heat resistance, strength and abrasion resistance all play an importantrole in the selection of materials used to make such fabrics. However,it is difficult to satisfy all of the foregoing desired properties.There is often a compromise between fire retardance and heat resistance,on the one hand, and strength and abrasion resistance, on the other.

Conventional fire retardant fabrics on the market typically rate veryhigh in one, or perhaps two, of the foregoing desired properties. Oneexample is a proprietary fabric aramid fabric sold by DuPont, whichrates high in strength and abrasion resistance at room temperature butonly provides protection against high temperatures and flame for arelatively short period of time. When exposed to direct flame, theleading m-aramid “fire retardant” fabric begings to shrink and char inas little as 3 seconds, and the degradation of the fabric increases asthe duration of exposure increases. Ironically, it is the tendency ofm-aramid fabrics to char and shrink that is purported to protect thewearer's skin from heat and flame. M-aramid fabrics may protect thewearer from burns for several seconds, but becomes essentially worthlessas a protective shield after it has begun to char, shrink and decompose.Once this occurs, large holes can open up through which flame and heatcan pass, thus burning, or even charring, the naked skin of the personwearing the fabric. Fabrics based on p-aramid are also strong and resistabrasion at room temperature but also char and shrink when exposed toflame or high temperature.

Flammable fabrics such as cotton, polyester, rayon, and nylon have beentreated with a fire retardant finish to enhance fire retardance. Whilethis may temporarily increase the flame retardant properties of suchfabrics, typical fire retardant finishes are not permanent. Exposure ofthe treated fabric to UV radiation (e.g., sun light) as well as routinelaundering of the fabric can greatly reduce the fire retardantproperties of the fabric. The user may then have a false sense ofsecurity, thus unknowingly exposing himself to increased risk of burns.There may be no objective way to determine, short of being caught in afiery conflagration, whether a treated garment still possessessufficient fire retardance to offset the risks to which the wearer maybe exposed.

More recently, a range of highly fire retardant and heat resistant yarnsand fabrics comprised of oxidized polyacrylonitrile fibers blended withone or more strengthening fibers were developed. Yarns and fabrics madeexclusively from oxidized polyacrylonitrile fibers lack adequatestrength for use in many applications. Blending oxidizedpolyacrylonitrile fibers with one or more types of strengthening fibersyields yarns and fabrics having increased strength and flexibility. U.S.Pat. Nos. 6,287,686 and 6,358,608 to Huang et al. disclose a range ofyarns and fabrics that preferably include about 85.5-99.9% by weightoxidized polyacrylonitrile fibers and about 0.1-14.5% by weight of oneor more strengthening fibers. U.S. Pat. No. 4,865,906 to Smith, Jr.includes about 25-85% oxidized polyacrylonitrile fibers combined with atleast two types of strengthening fibers. For purposes of teaching fireretardant and heat resistant yarns, fabrics and articles of manufacture,the foregoing patents are incorporated herein by reference.

Highly flame retardant and heat resistant fabrics made according to theHuang et al. patents are sold under the name CARBONX by Chapman ThermalProducts, Inc., located in Salt lake City, Utah. Such fabrics are ableto resist burning or charring even when exposed to a direct flame.Fabrics made according to the Huang et al. and Smith, Jr. patents arenot only superior to NOMEX as far as providing fire retardance and heatresistance, they are softer, have higher breathability, and are betterat absorbing sweat and moisture. CARBONX feels much like an ordinaryfabric made from natural or natural feeling synthetic fibers. M-aramidfabric, in contrast, feels more like wearing a plastic sheet than afabric since it does not breathe well, nor does it wick sweat andmoisture but sheds it readily. Unfortunately, the aspect of CARBONX thatmakes it feel most like an ordinary fabric—its ability to absorb sweat,moisture and liquid—does not aid in shedding a flammable liquid.

Some applications may require a level of tensile strength, abrasionresistance, and durability not provided by conventional fire retardantfabrics. One way to improve such features is to incorporate a metallicfilament, such as is disclosed in U.S. Pat. No. 6,800,367 to Hanyon etal., the disclosure of which is incorporated by reference. Including ametal filament also increases the cut resistance of the fabric.Nevertheless, adding a metallic filament may increase the ability of afabric to transfer heat, and it does not appreciably increase theability of the fabric to shed flammable liquids.

Accordingly, it would be an advancement in the art to provide fireretardant and heat resistant yarns that were able to maintain a highlevel of fire retardance and heat resistance while having improvedtensile strength, abrasion resistance, durability, and liquid sheddingcapabilities.

BRIEF SUMMARY OF THE INVENTION

The present invention encompasses novel yarns and fabrics that include ahigh concentration of oxidized polyacrylonitrile (O-Pan) fibers, whichmaintain a high level of fire retardance and heat resistance, while alsopossessing improved tensile strength, abrasion resistance, durability,and the ability to shed liquids and gels. The inventive yarns includeO-Pan fibers, typically combined with one or more strengthening fibers,and are encapsulated by a liquid-resistant and strengthening coating,such as a silicone polymer. Encapsulating the fire retardant and heatresistant yarn with a silicone polymer increases the tensile strength,abrasion resistance, durability, and liquid and gel shedding capabilityof the yarn, as well as fabrics and articles made from such yarn.Encapsulating the yarn, rather than coating the whole fabric, not onlyseals the individual yarn strands in superior fashion, it also maintainsbreathability of the fabric as a whole rather than forming animpermeable barrier. This greatly improves performance and comfort whenworn against a person's body.

The present invention combines the tremendous fire retardant and heatresistant characteristics of yarns made from O-Pan fibers with thestrengthening and liquid and gel shedding properties imparted by aliquid resistant polymer coating. Simply encapsulating the yarn of aconventional flammable fabric with a silicone polymer coating cannotyield a fabric having a flame retardance and heat resistance that iseven remotely similar to the level provided by O-Pan based fabrics.Moreover, encapsulating aramid-based materials with a liquid-resistantand strengthening silicone polymer coating does not alter the inherenttendency of fabrics formed from such materials to char, shrink, and formholes when exposed to direct flame and/or heated to above 600° F. Onlyby combining the tremendous fire retardant and heat resistant propertiesof O-Pan based fabrics with the strengthening aspects and liquid and gelshedding capabilities offered by liquid-resistant and strengtheningpolymer encapsulation can true synergy be obtained (i.e., the ability toprovide the highest level of fire retardance and heat resistance to afabric, while also providing enhanced tensile strength, abrasionresistance, durability, and liquid and gel shedding capabilities, all ofwhich synergistically contribute to the ability of the fabric to protecta wearer from fire and heat).

The failure to provide all of these features in a single fabric cangreatly undermine the otherwise excellent protection from fire. Forexample, even though conventional CARBONX fabrics provide superiorprotection against fire, heat and burns compared to other leading fireresistant fabrics such as the leading aramid “fire retardant” fabrics,such protection can be compromised if the fabric lacks sufficienttensile strength, abrasion resistance and durability for a givenapplication. The fabric will typically only protect the wearer to theextent the fabric is able to maintain its structural integrity whenprotection is needed most, i.e., a fabric designed to protect the skinadvantageously remains positioned between the wearer's body and the heatsource to provide maximum protection. An inadvertent hole or tear canprovide a conduit through which heat and flame can breach the otherwisecontinuous protective shield. Because of the generally weaker nature ofO-Pan based fabrics compared to conventional fabrics, encapsulating theyarn comprising O-Pan based fabrics with a strengthening polymerprovides a much greater incremental benefit with regard to tensilestrength, abrasion resistance, and durability compared to conventionalfabrics which are stronger to begin with. Encapsulation of the O-Panbased yarn with a liquid-shedding polymer also greatly increases theability of the O-Pan based fabric to shed liquids and gels, includingflammable liquids and gels.

Thus, encapsulating the yarn of O-Pan based fabrics with aliquid-resistant and strengthening polymer reduces the tendency of suchfabrics to form holes or tears while protecting the wearer from flameand heat, and it helps such fabrics to shed liquids and gels, includingflammable liquids and gels that can engulf the wearer in flames ifabsorbed into the fabric. Encapsulation of the O-Pan based yarn with aliquid-resistant and strengthening polymer coating greatly increases therange of situations where O-Pan based fabrics can provide superiorprotection from heat and flame as intended, even though theliquid-shedding and strengthening polymer may not itself provide anysignificant incremental heat or flame resistance beyond that which isalready provided by the O-Pan based fabric. The high level of heat andflame resistance is provided mainly or exclusively by the O-Pan basedfabric. The encapsulation of the O-Pan yarn comprising the fabric with aliquid-resistant and strengthening polymer coating mainly provides theauxiliary benefits of increased tensile strength, abrasion resistance,durability, and liquid and gel shedding capability (e.g., flammableliquids and gels). Nevertheless, the overall protection to the weareragainst flame and heat is greatly enhanced by the auxiliary benefitsimparted by encapsulating the yarn with a liquid-resistant andstrengthening polymer coating, demonstrating the synergistic effect ofcombining O-Pan based fabrics with polymer encapsulation of the yarncomprising the fabric.

Additional strength and abrasion resistance can be provided by blendingone or more types of strengthening fibers with the O-Pan fibers used tomake the yarn. Strengthening fibers do not possess the level of fireretardance and heat resistance as 0-Pan fibers but can be used tostrengthened the yarn while maintaining an adequate level of fireretardance and heat resistance in the yarn. Exemplary “strengtheningfibers” include, but are not limited to, polybenzimidazole (PBI),polybenzoxazole (PBO), polyphenylene-2,6-benzobisoxazole (PBO),modacrilic, p-aramid, m-aramid, polyvinyl halides, wool, fire resistantpolyesters, fire resistant nylons, fire resistant rayons, cotton, andmelamine. The oxidized polyacrylonitrile fibers and the strengtheningfibers are each first preferably carded into respective strands orcarded together to form a blended strand. Multiple strands may then beintertwined together to form a yarn. Alternatively, the yarn may includestrengthening filaments made from the same materials as the foregoingstrengthening fibers. Even ceramic or metal filaments may be included,though they may be unnecessary in view of the greatly increased tensilestrength, abrasion resistance and durability imparted by encapsulatingthe yarn with the liquid-shedding polymer.

Exemplary liquid-resistant and strengthening polymer coatings include awide variety of curable silicone-based polymers and polysiloxanes. Suchpolymers are typically encapsulated over the individual yarn strands ofa tensioned fabric that is drawn through a bath of shear thinned polymerresin. Thereafter, the polymer resin is cured to form the finalencapsulated yarn. The process advantageously only encapsulates the yarnstrands but leaves spaces between the yarn strands that are woven orknitted together so as to permit the treated fabric to breathe. In thisway, the treated fabric still feels and behaves more like an ordinaryfabric rather than a laminate sheet or plugged fabric.

In general, the yarn is typically encapsulated with the liquid-resistantand strengthening coating after being woven or knitted into a fabric.Nevertheless, it is within the scope of the invention to encapsulate theyarn before forming it into a fabric. Individual yarn strands can beencapsulated by drawing them through a bath of shear thinned polymercomposition and then curing the polymer. The treated yarn strands maythen be knitted, woven or otherwise joined together to form a desiredfabric.

Examples of articles of manufacture made using the liquid-resistantpolymer treated O-Pan yarns and fabrics include clothing, jump suits,gloves, socks, welding bibs, fire blankets, padding, protective headgear, linings, undergarments, bedding, drapes, and the like.

According to one embodiment, the yarn or fabric may be pre-treated witha fluorochemical prior to encapsulation with the shear thinned polymercoating. Pre-treatment with a fluorochemical may assist in helping thepolymer encapsulated yarn or fabric repel or shed liquids and gels, suchas water and hydrocarbons. The fluorochemical may advantageously beapplied as a suspension or solution in combination with a solvent thatis driven off by evaporation. Thereafter, the silicone polymer isapplied to the yarn or fabric in order to encapsulate the yarn strands.The fluorochemical is at least partially impregnated into the yarn.

These and other objects and features of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of the invention as set forthhereinafter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS I. Introduction andDefinitions.

The present invention encompasses fire retardant and heat resistantyarns and fabrics in which the yarn is encapsulated by aliquid-resistant and strengthening coating to yield fabrics and articlesthat provide better tensile strength, abrasion resistance, durability,and the ability to shed liquids and gels compared to fabrics in theabsence of such yarn encapsulation. Encapsulating the individual yarnstrands, rather than coating and plugging the whole fabric, not onlyseals the individual yarn strands in superior fashion, it also maintainsbreathability of the fabric.

By combining the tremendous fire retardant and heat resistant propertiesof O-Pan based fabrics with the strengthening and liquid-sheddingaspects offered by encapsulation a synergistic combination is obtained(i.e., the high level of fire retardance and heat resistance of thefabric, coupled with enhanced tensile strength, abrasion resistance,durability, and liquid-shedding capabilities of the encapsulation,synergistically contribute to the ability of the fabric to protect awearer from fire and heat). The failure to provide all of these featuresin a single fabric can greatly undermine the otherwise excellentprotection from fire, i.e., the fabric will typically only protect thewearer to the extent the fabric is able to maintain its structuralintegrity when protection is needed most. Because of the generallyweaker nature of O-Pan based fabrics compared to conventional fabrics,encapsulating the yarn comprising O-Pan based fabrics provides a muchgreater incremental benefit with regard to tensile strength, abrasionresistance, and durability compared to conventional fabrics which arestronger to begin with. Encapsulation of the O-Pan based yarn alsogreatly increases the ability of the O-Pan based fabric to shed liquidsand gels, including flammable liquids and gels.

The term “Limiting Oxygen Index” (or “LOI”) is defined as the minimumconcentration of oxygen necessary to support combustion of a material.The LOI is primarily a measurement of flame retardancy rather thantemperature resistance. Temperature resistance is typically measured asthe “continuous operating temperature”.

The term “continuous operating temperature” measures the maximumtemperature, or temperature range, at which a particular fabric willmaintain its strength and integrity over time when exposed to constantheat of a given temperature or range. For instance, a fabric that has acontinuous operating temperature of 400° F. can be exposed totemperatures of up to 400° F. for prolonged periods of time withoutsignificant degradation of fiber strength, fabric integrity, andprotection of the user. In some cases, a fabric having a continuousoperating temperature of 400° F. may be exposed to brief periods of heatat higher temperatures without significant degradation. The presentlyaccepted standard for continuous operating temperature in the autoracing industry rates fabrics as being “flame retardant” if they have acontinuous operating temperature of between 375° F. to 600° F.

The term “fire retardant” refers to a fabric, felt, yarn or strand thatis self extinguishing. The term “nonflammable” refers to a fabric, felt,yarn or strand that will not burn.

The term “Thermal Protective Performance” (or “TPP”) relates to afabric's ability to provide continuous and reliable protection to aperson's skin beneath a fabric when the fabric is exposed to a directflame or radiant heat. The TPP measurement, which is derived from acomplex mathematical formula, is often converted into an SFI rating,which is an approximation of the time it takes before a standardquantity of heat causes a second degree burn to occur.

The term “SFI Rating” is a measurement of the length of time it takesfor someone wearing a specific fabric to suffer a second degree burnwhen the fabric is exposed to a standard temperature. The SFI Rating isprinted on a driver's suit. The SFI Rating is not only dependent on thenumber of fabric layers in the garment, but also on the LOI, continuousoperating temperature and TPP of the fabric or fabrics from which agarment is manufactured. The standard SFI Ratings are as follows:

SFI Rating Time to Second Degree Burn 3.2A/1  3 Seconds 3.2A/3  7Seconds 3.2A/5 10 Seconds 3.2A/10 19 Seconds 3.2A/15 30 Seconds 3.2A/2040 Seconds

A secondary test for flame retardance is the after-flame test, whichmeasures the length of time it takes for a flame retardant fabric toself extinguish after a direct flame that envelopes the fabric isremoved. The term “after-flame time” is the measurement of the time ittakes for a fabric to self extinguish. According to SFI standards, afabric must self extinguish in 2.0 seconds or less in order to pass andbe certifiably “flame retardant”.

The term “tensile strength” refers to the maximum amount of stress thatcan be applied to a material before rupture or failure. The “tearstrength” is the amount of force required to tear a fabric. In general,the tensile strength of a fabric relates to how easily the fabric willtear or rip. The tensile strength may also relate to the ability of thefabric to avoid becoming permanently stretched or deformed. The tensileand tear strengths of a fabric should be high enough so as to preventripping, tearing, or permanent deformation of the garment in a mannerthat would significantly compromise the intended level of thermalprotection of the garment.

The term “abrasion resistance” refers to the tendency of a fabric toresist fraying and thinning during normal wear. Although related totensile strength, abrasion resistance also relates to other measurementsof yarn strength, such as shear strength and modulus of elasticity, aswell as the tightness and type of the weave or knit.

The terms “fiber” and “fibers” refers to any slender, elongatedstructure that can be carded or otherwise formed into a thread. Fiberstypically have a length of about 2 mm to about 25 mm and an aspect ratioof at least about 100:1. Examples include “staple fibers”, a term thatis well-known in the textile art. The term “fiber” differs from the term“filament”, which is defined separately below and which comprises adifferent component of the inventive yarns.

The term “thread”, as used in the specification and appended claims,shall refer to continuous or discontinuous elongated strands formed bycarding or otherwise joining together one or more different kinds offibers.

The term “filament” shall refer to a thread of indefinite length,whether comprising multiple fibers or a monofilament.

The term “yarn” shall refer to a continuous strand comprises of amultiplicity of fibers, filaments, or the like in bundled form, such asmay be suitable for knitting, weaving or otherwise used to form afabric.

The term “fabric” shall refer to an article of manufacture formed byknitting, weaving or otherwise joining a plurality of yarn strandstogether to form a multi-dimensional structure used to manufacture awide variety of useful articles.

The terms “encapsulate” and “outer shell” shall refer to the positioningor placement of a liquid-shedding polymer material around an inner corecomprising a yarn strand, before or after the yarn is formed into afabric. The terms “encapsulate” and “outer shell” refer to the fact thatat least some of the liquid-shedding polymer material is located on anouter perimeter of the yarn strand(s). They do not mean that some of theliquid-shedding polymer material that “encapsulates” the inner yarn corecannot also be located in interstitial spaces or pores within the inneryarn core.

The term “inner core” shall refer to the fire retardant and heatresistant yarn that is encapsulated by the liquid-resistant andstrengthening polymer shell comprising the “outer shell”.

II. Fire Retardant and Heat Resistant Yarns and Fabrics.

Fire retardant and heat resistant yarns according to the inventiontypically comprise at least one type of fire retardant and heatresistant fibers and/or filaments, preferably combined or blended withat least one type of strengthening fibers and/or filaments. Fireretardant and heat resistant fibers can be carded into a thread, eitheralone or in combination with one or more types of strengthening fibers.Multiple threads can be twisted or braided together to form a yarnstrand. One or more fire retardant and heat resistant threads comprisingmainly or solely fire retardant and heat resistant fibers or filament(s)can be twisted or braided together with one or more strengtheningstrands comprising mainly or solely strengthening fibers and/orfilament(s). Because a yarn strand typically consists of multiplestrands twisted or braded together, it will typically include asubstantial amount of interstitial space between the individual strands,at least before being encapsulated by the liquid-shedding polymer.

Fabrics comprising the fire retardant and heat resistant yarns can beformed by knitting, weaving or otherwise combining multiple strands ofyarn together. Any known method of forming a fabric from a yarn can beutilized to form the inventive fire retardant and heat resistantfabrics. Exemplary fire retardant and heat resistant yarns, fabrics andarticles that can be improved according to the present invention aredisclosed in U.S. Pat. Nos. 6,287,686, 6,358,608, 6,800,367 and4,865,906. For purposes of disclosing fire retardant and heat resistantyarns and fabrics capable of being encapsulated according to theinvention, the disclosures of the foregoing patents are incorporated byreference.

A. Fire Retardant and Heat Resistant Fibers and Filaments

Exemplary fire retardant and heat resistant fibers and filaments aremade from oxidized polyacrylonitrile (O-Pan). The O-Pan fibers orfilaments within the scope of the invention may comprise any type ofO-Pan having high fire retardance and heat resistance. In a preferredembodiment, O-Pan is obtained by heating polyacrylonitrile (e.g.,polyacrylonitrile fibers or filaments) in a cooking process betweenabout 180° C. to about 3000° C. for at least about 120 minutes. Thisheating/oxidation process is where the polyacrylonitrile receives itsinitial carbonization. Preferred O-Pan fibers and filaments have an LOIof about 50-65. In most cases, O-Pan made in this way may be consideredto be nonflammable.

Examples of suitable O-Pan fibers include LASTAN, manufactured by AshiaChemical in Japan; PYROMEX, manufactured by Toho Rayon in Japan; PANOX,manufactured by SGL; and PYRON, manufactured by Zoltek. It is alsowithin the scope of the invention to utilize filaments that compriseO-Pan.

In general, it is believed that fabrics which include a substantialamount of O-Pan fibers and/or filaments will resist burning, even whenexposed to intense heat or flame exceeding 3000° F., because the O-Panfibers carbonize and expand, thereby eliminating any oxygen contentwithin the fabric necessary for combustion of the more readilycombustible strengthening fibers. In this way, the O-Pan fibers orfilaments provide a combustion shield that makes the less fire retardantsubstances in the yarn or fabric act like better fire retardantsubstances.

One of skill in the art will appreciate that other fire retardant andheat resistant materials can be used in addition to, or in place of,O-Pan so long as they have fire retardant and heat resistance propertiesthat are comparable to those of O-Pan. By way of example, polymers orother materials having an LOI of at least about 50 and which do not burnwhen exposed to heat or flame having a temperature of about 3000° F.could be used in addition to, or instead of, O-Pan.

The fire retardant and heat resistant yarn comprising the inner core ofthe overall liquid and gel shedding yarn, fabric or article may consistsolely of O-Pan fibers or filaments. When the O-Pan is blended with oneor more strengthening fibers or filaments, O-Pan is preferably includedin an amount in a range of about 25% to about 99.9% by weight of theinner core, more preferably in a range of about 40% to about 95% byweight, and most preferably in a range of about 50% to about 90% byweight of the inner core.

B. Strengthening Fibers and Filaments

Strengthening fibers and filaments that may be incorporated into fireretardant and heat resistant yarns, fabrics and articles of the presentinvention may comprise any fiber or filament known in the art. Ingeneral, preferred strengthening fibers will be those that have arelatively high LOI and TPP compared to natural organic fibers such ascotton, although the use of such fibers is within the scope of theinvention. The strengthening fibers preferably have an LOI greater thanabout 20.

Strengthening fibers may be carded or otherwise formed into threads,either alone or in combination with other fibers (e.g, O-Pan fibers).Strengthening threads or filaments may be twisted, braided or otherwisecombined with fire retardant and heat resistant strands to form ablended yarn.

Strengthening fibers and filaments within the scope of the inventioninclude, but are not limited to, polybenzimidazole (PBI),polybenzoxazole (PBO), polyphenylene-2,6-benzobisoxazole (PBO),modacrilic, p-aramid, m-aramid, polyvinyl halides, wool, fire resistantpolyesters, fire resistant nylons, fire resistant rayons, cotton, linen,and melamine. By way of comparison with O-Pan, which has an LOI of about50-65, the LOI's of selected strengthening fibers are as follows:

PBO 68 PBI 35–36 modacrylic 28–32 m-Aramid 28–36 p-Aramid 27–36 wool 23polyester 22–23 nylon 22–23 rayon 16–17 cotton 16–17

Examples of suitable p-aramids include KEVLAR, manufactured by DuPont;TWARON, manufactured by Twaron Products BB; and TECKNORA, manufacturedby Teijin. Examples of suitable m-aramids include NOMEX, manufactured byDuPont; CONEX, manufactured by Teijin; and P84, an m-aramid yarn with amulti-lobal cross-section made by a patented spinning method,manufactured by Inspec Fiber. For this reason P84 has better fireretardant properties compared to NOMEX.

An example of a PBO is ZYLON, manufactured by Toyobo. An example of aPBI fiber is CELAZOLE of PBI Performance Products, Inc. An example of amelamine fiber is BASOFIL. An example of a fire retardant or treatedcotton is PROBAN, manufactured by Westex. Another is FIREWEAR.

Strengthening fibers and filaments may be incorporated in the yarns ofthe present invention in at least the following ways: (1) as one or morestrengthening filaments twisted, wrapped, braided or otherwise joinedtogether with threads or filaments comprising oxidizedpolyacrylonitrile; or (2) as fibers blended with O-Pan fibers into oneor more threads.

In short, strengthening fibers may be added to the inventive yarns inthe form of strengthening threads comprising one or more different typesof strengthening fibers, a ended thread comprising O-Pan fibers and oneor more different types of strengthening fibers, or as a strengtheningfilament. When O-Pan is blended with one or more strengthening fibers orfilaments, the strengthening fibers or filaments are preferably includedin an amount in a range of about 0.1% to about 75% by weight of theinner core, more preferably in a range of about 5% to about 60% byweight, and most preferably in a range of about 10% to about 50% byweight of the inner core.

C. Metallic and Ceramic Filaments

Yarns according to the invention may include one or more types ofmetallic or ceramic filaments in order to increase cut resistance,tensile strength and abrasion resistance. Metallic filaments typicallyhave the highest combination of tensile strength and cut resistance butalso conduct heat more rapidly. Examples of metals used to form highstrength filaments include, but are not limited to, stainless steel,stainless steel alloys, other steel alloys, titanium, aluminum, copper,and the like.

Examples of high strength ceramic filaments include silicon carbide,graphite, silica, aluminum oxide, other metal oxides, and the like.Examples of high strength and heat resistant ceramic filaments are setforth in U.S. Pat. Nos. 5,569,629 and 5,585,312 to TenEyck et al., whichdisclose ceramic filaments that include 62-85% by weight SiO₂, 5-20% byweight Al₂O₃, 5-15% by weight MgO, 0.5-5% by weight TiO_(x), and 0-5%ZrO₂. High strength and flexible ceramic filaments based on a blend ofone or oxides of Al, Zr, Ti, Si, Fe, Co, Ca, Nb, Pb, Mg, Sr, Cu, Bi andMn are disclosed in U.S. Pat. No. 5,605,870 to Strom-Olsen et al. Forpurposes of disclosing high strength ceramic filaments, the foregoingpatents are incorporated herein by reference. Fiberglass filaments canalso be used. Strengthening filaments preferably have a diameter in arange of about 0.0001″ to about 0.01″, more preferably in a range ofabout 0.0005″ to about 0.008″, and most preferably in a range of about0.001″ to about 0.006″. Yarns containing a high concentration ofoxidized polyacrylonitrile fibers that are generally too weak to be usedin the manufacture of fire retardant and heat resistant fabrics can begreatly strengthened with even small percentages of one or more metallicfilaments, and fabrics manufactured therefrom have been found to besurprisingly strong.

In general, where it is desired to maximize the strength of thematerial, it will be preferable to maximize the volume of strengtheningfilaments that are added to the yarn. However, it will be appreciatedthat as the amount of strengthening filaments increases in the yarn, theheat resistance generally declines. As a practical matter, the fireretardant and heat resistant requirements of the resulting yarn, fabricor other fibrous blend will determine the maximum amount ofstrengthening filaments that can be added to the yarn.

III. Liquid-Shedding and Strengthened Fire Retardant and Heat ResistantYarns and Fabrics.

The fire retardant and heat resistant yarns and fabrics discussed abovecan be treated according to the invention by encapsulating the yarn witha liquid-shedding and strengthening polymer coating material. Theliquid-shedding and strengthening polymer coating yields yarns, fabricsand articles that are much better at shedding liquids and gels, such asflammable liquids and gels. In this way, thermal protection to thewearer is further increased when used to protect a wearer exposed toflammable liquids or gels. In addition, polymer encapsulationsignificantly increases the tensile strength, abrasion resistance anddurability of the first retardant and heat resistant yarns, fabrics andarticles of the invention. Increasing the tensile strength, abrasionresistance and durability of a fabric or article also increases thethermal protection of the wearer by reducing the formation of holes orrips through the fabric and increasing the continuity of protection.

Exemplary liquid-shedding and strengthening polymer materials, optionalcompositions applied to yarns in addition to the liquid-shedding andstrengthening polymer materials, as well as methods for encapsulatingyarns with the liquid-shedding and strengthening polymer materials, aredisclosed in U.S. Pat. Nos. 4,666,765, 5,004,643, 5,209,965, 5,418,051,5,856,245, 5,869,172, 5,935,637, 6,040,251, 6,071,602, 6,083,602,6,129,978, 6,289,841, 6,312,523, 6,342,280, and 6,416,613. For purposesof disclosing liquid-shedding and strengthening polymer coatingmaterials, as well as methods of applying such materials to a fabric,the disclosures of the foregoing patents are incorporated by reference.

Exemplary liquid-resistant and strengthening polymer coatings include awide variety of curable silicone-based polymers and polysiloxanes. Suchpolymers are typically applied as an uncured or partially cured polymerresin and then cured (i.e., cross-linked and/or further polymerized)after encapsulating the yarn being treated. The polymer resins beforeapplication typically have a viscosity in a range of about 1000 cps toabout 2,000,000 cps at a shear rate of 1/10 s and a temperature of 25°C. The polymer resins preferably have a viscosity in a range of about5000 cps to about 10,000 cps at a shear rate of 1/10 s and a temperatureof 25° C. In a most preferred embodiment, such polymer resins preferablycontain less than about 1% by weight of volatile material. When cured,the encapsulating polymers are preferably elastomeric in order to yielda generally flexible yarn, fabric or article.

A preferred class of liquid curable silicone polymer compositionscomprises a curable mixture of the following components: (1) at leastone organo-hydrosilane polymer or copolymer; (2) at least one vinylsubstituted polysiloxane polymer or copolymer; (3) a platinum orplatinum containing catalyst; and (4) optionally fillers and additives.

Typical silicone hydrides (component 1) are polymethylhydrosiloxaneswhich are dimethyl siloxane copolymers. Typical vinyl terminatedsiloxanes are vinyl-dimethyl terminated or vinyl substitutedpolydimethyl siloxanes. Typical catalyst systems include solutions orcomplexes of chloroplatinic acid in alcohols, ethers, divinylsiloxanes,and cyclic vinyl siloxanes.

Particulate fillers can be included to extend and reinforce the curedpolymer composition and also improve the thixotropic behavior of theuncured polymer resins.

Exemplary silicone polymer resins that may be used to encapsulate fireretardant and heat resistant yarns according to the invention include,but are not limited to, SILOPREN LSR 2530 and SILOPREN LSR 2540/01,which comprise a vinyl-terminated polydimethyl/siloxane with fumedsilica and methylhydrogen siloxane, which are available from MobayChemical Co.; SILASTIC 595 LSR, a polysiloxane available from DowCorning; SLE 5100, SLE 5110, SLE 5300, SLE 5500, and SLE 6108, which arepolysiloxanes, and SLE 5106, a siloxane resin solution, all availablefrom General Electric; KE 1917 and DI 1940-30, silicone polymersavailable from Shin-Etsu; LIQUID RUBBER BC-10, a silicone fluid withsilicone dioxide filler and curing agents, available from SWS SiliconesCorporation.

The foregoing silicone polymer resins are characterized as having highviscosity. In order for such polymer resins to properly encapsulate theyarn, they must typically be thinned in some manner to reduce theviscosity so as to flow around the yarn and at least partially penetrateinto the interstitial spaces within the yarn. This may be accomplishedin any desired manner. According to one embodiment, the polymer resinsare subjected to high shearing conditions, which causes them to undergoshear thinning and/or thixotropic thinning. Any suitable mixing blade,combination of blades, or other apparatus capable of applying high shearmay be introduced into the vessel containing the polymer resin in orderto temporarily reduce the viscosity of the resin before or duringapplication to the yarn or fabric.

Such polymers are typically encapsulated over the individual yarnstrands of a tensioned fabric that is drawn through a bath of shearand/or thixotropically thinned polymer resin. Thereafter, the polymerresin is cured to form the final encapsulated yarn. Curing may becarried out using heat to accelerate polymerization and/or cross-linkingor the polymer resin. The process advantageously only encapsulates theyarn strands but leaves spaces between the yarn strands that are wovenor knitted together so as to permit the treated fabric to breathe. Inthis way, the treated fabric still feels and behaves more like anordinary fabric rather than a laminate sheet or plugged fabric.

According to one embodiment, the silicone polymer resin is blended witha benzophenone (e.g., about 0.3-10 parts by weight of the siliconepolymer), examples of which include 2,4-dihydroxybenzophenone (e.g.,UVINUL 400, available from BASF), 2-hydroxy-4-methoxybenzophenone (e.g.,UVINUL M-40, available from BASF), 2,2′,4,4′-tetrahydroxybenzophenone(e.g., UVINUL D-50, available from BASF),2,2′-dihydroxy-4,4′-dimethoxybenzophenone (e.g., UVINUL D-49, availablefrom BASF), mixed tetra-substituted benzophenones (e.g., UVINUL 49 D,available from BASF), and 2-ethylhexyl-2-cyano-3,3-diphenylacrylate(e.g., UVINUL N-539, available from BASF).

The silicone polymer resin may also be blended with an accelerator(e.g., Dow Corning 7127 accelerator, a proprietary polysiloxanematerial) (e.g., 5-10 parts by weight of the silicone polymer resin)just before being applied to the yarn or fabric to promote curing.

The silicone polymer resin may further include various additives inorder to impart desired properties to the yarn or fabric. Exemplaryadditives include UV absorbers, flame retardants, aluminum hydroxide,filling agents, blood repellants, flattening agents, optical reflectiveagents, hand altering agents, biocompatible proteins, hydrolyzed silk,and agents that affect thermal conductivity, radiation reflectivity,and/or electrical conductivity.

In general, the yarn is typically encapsulated with the liquid-resistantcoating after being woven or knitted into a fabric. Nevertheless, it iswithin the scope of the invention to encapsulate the yarn before formingit into a fabric. One or more individual yarn strands can beencapsulated by drawing them through a bath of shear thinned polymercomposition and then curing the polymer. The treated yarn strands maythen be knitted, woven or otherwise joined together to form a desiredfabric.

The silicone polymer coating is preferably applied to the yarn or fabricin an amount in a range of about 5% to about 200% by weight of theoriginal yarn or fabric inner core, more preferably in an amount in arange of about 10% to about 100% by weight of the original yarn orfabric inner core.

Yarns and fabrics may also be advantageously pre-treated with afluorochemical prior to being encapsulated by the silicone polymer resinin order to further increase the liquid and gel shedding properties ofthe yarn or fabric. Exemplary fluorochemical compositions include, butare not limited to, MILEASE F-14N, F-34, F-31× and F-53 sold by ICIAmericas, Inc.; PHOTOTEX FC104, FC461, FC731, FC208 AND FC232 sold byCiba/Geigy; TEFLON polymers such as TEFLON G, NPA, SKF, UP, UPH, PPR, Nand MLV, sold by DuPont; ZEPEL polymers such as ZEPEL B, D, K, RN, RC,OR, HT, 6700 AND 7040, also from DuPont; SCOTCHGUARD sold by 3M.

MILEASE F-14 contains approximately 18% perfluoroacrylate copolymer, 10%ethylene glycol, 7% acetone, and 65% water. MILEASE F-31X is adispersion of fluorinated resin, acetone and water. ZEPEL 6700 iscomprised of 15-20% perfluoroalkyl acrylic copolymer, 1-2% alkoxylatedcarboxylic acid, 3-5% ethylene glycol, and water, and has a pH of 2-5.ZEPEL 7040 is similar to ZEPEL 6700 but further contains 7-8% acetone.SCOTCHGUARD is comprised of aqueously dispersed fluorochemicals inpolymeric form.

Liquid repellant fluorochemical compositions are saturated into thefabric or yarn to completely and uniformly wet the fabric or yarn. Thismay be performed by dipping the fabric or yarn in a bath of liquidcomposition or padding the composition onto and into the fabric or yarn.After applying the fluorochemical composition to the fabric or yarn, thewater (or other liquid carrier) and other volatile components of thecomposition are removed by conventional techniques to provide a treatedfabric or yarn that is impregnated with the dried fluorochemical. In oneembodiment, the saturated fabric or yarn is compressed to remove excesscomposition. It is then heated to remove the carrier liquid byevaporation (e.g., at a temperature of about 130-160° C. for a period oftime about 2-5 minutes). If the fluorochemical is curable, heating mayalso catalyze Oz or trigger curing.

The fluorochemical may also contain a bonding agent in order tostrengthen the bond between the fluorochemical and the yarn or fabric towhich it is applied. Exemplary bonding agents include Mobay SILOPRENbonding agent type LSR Z 3042 and NORSIL 815 primer.

When included, the fluorchemical is preferably applied in an amount in arange of about 1% to about 10% by weight of the original yarn or fabricinner core, more preferably in an amount in a range of about 2% to about4% by weight of the original yarn or fabric inner core.

IV. EXAMPLES

The following examples are provided in order to illustrate variousembodiments of the invention. Although the examples are written inpresent tense and are therefore hypothetical in nature, they are basedon testing of a fabric comprising a 70:30 wt % blend of O-Pan andp-aramid that was coated with a proprietary silicone-based polymercoating owned by Nextec Applications Inc., based in Vista, Calif. at therequest of the inventor. The examples therefore have a high degree ofpredictive value based on test results conducted by the inventor.

Example 1

A fire retardant and heat resistant fabric made from a yarn having a70:30 wt % blend of O-Pan and p-aramid, respectively, is encapsulatedwith a liquid shedding and strengthening silicone-based polymer asfollows. First, the fabric is placed under tension. Second, thetensioned fabric is drawn through a vessel containing a silicone-basedpolymer resin. Third, the silicone-based polymer resin is subjected tolocalized shear-thinning forces produced by a rapidly spinning shearingblade adjacent to a surface of the fabric in order for the shear-thinnedresin to encapsulate the yarn of the fabric and at least partiallypenetrate into interstitial spaces of the yarn. The viscosity of thesilicone-based polymer resin is sufficiently low that it does not plugthe spaces between the individual yarn strands of the fabric. Fourth,the treated tensioned fabric is removed from the vessel containing thesilicone-based polymer resin. Fifth, the treated fabric is heated inorder to cure the silicone-based polymer resin and form thestrengthening and liquid-shedding coating over the yarn.

The resulting fire retardant and heat resistant fabric comprisingsilicone polymer encapsulated yarn has increased tensile strength,abrasion resistance, durability and liquid- and gel-shedding capabilitycompared to the fire retardant and heat resistant fabric in the absenceof the silicone polymer. The fabric is therefore better able to protecta person wearing the fabric when exposed to fire, heat and a flammableliquid or gel compared to the fire retardant and heat resistant fabricprior to being encapsulated with the silicone polymer by better sheddingthe flammable liquid or gel and resisting formation of holes through thefabric, thus providing greater continuity of fabric between the wearer'sskin and the fire, heat and any remaining flammable liquid or gel.Because the silicone polymer only encapsulates the individual yarnstrands comprising the fabric, but does not plug the holes or spacesbetween the yarn strands, the treated fabric remains porous and is ableto breathe.

Example 2

A fire retardant and heat resistant fabric made from a yarn having a60:20:20 wt % blend of O-Pan, p-aramid, and m-aramid, respectively, istreated in the manner discussed in Example 1. The resulting fabric issomewhat stronger and more durable than the fabric obtained in Example 1as a result of including a blend of strengthening fibers.

Example 3

A fire retardant and heat resistant fabric made from a yarn consistingof 100% O-Pan is treated in the manner discussed in Example 1. Eventhough the fabric made from 100% O-Pan is relatively weak and fragile,treatment with the silicone polymer greatly increases the tensilestrength, abrasion resistance, and durability so as to be acceptable forapplications for which the fabric would otherwise be unacceptable absentthe encapsulation treatment.

Example 4

A fire retardant and heat resistant fabric made from a yarn having a40:20:20:20 wt % blend of O-Pan, p-aramid, fire retardant wool, and PBI,respectively, is treated in the manner discussed in Example 1. Thisfabric is significantly stronger to begin with compared to the fabricsof Examples 1-3 as a result of include more strengthening fibers, but isless fire retardant and heat resistant.

Example 5

A fire retardant and heat resistant fabric made from a yarn having a60:40 wt % blend of O-Pan and m-aramid, respectively, is treated in themanner discussed in Example 1. This fabric is significantly stronger tobegin with compared to the fabrics of Example 1 as a result of includemore strengthening fibers, but is less fire retardant and heatresistant.

Example 6

A fire retardant and heat resistant fabric made from a yarn having a90:10 wt % blend of O-Pan and PBI, respectively, is treated in themanner discussed in Example 1. This fabric is not as strong as comparedto the fabrics of Examples 1, 2, 4 and 5 as a result of including lessstrengthening fibers, but is more fire retardant and heat resistant as aresult of including 10% PBI. Encapsulating this blend with the siliconepolymer coating greatly enhances its strength.

Example 7

A fire retardant and heat resistant fabric made from a yarn having a60:10:15:15 wt % blend of O-Pan, p-aramid, polyvinyl chloride, andm-aramid, respectively, is treated in the manner discussed in Example 1.This fabric is quite stronge as compared to previous examples as aresult of including more and more types of strengthening fibers, but isless fire retardant and heat resistant.

Examples 8-14

The fire retardant and heat resistant fabrics of Examples 1-7 arepretreated with a fluorochemical prior to encapsulation with thesilicone polymer. The flurochemical is saturated into the fabric as asolution or suspension with a solvent. Excess flurochemical compositionis removed from the saturated fabric by applying pressure. Thereafter,the flurochemical composition is heated in order to remove the solventby evaporation and dry the flurochemical. After applying the siliconepolymer according to Example 1, the flurochemical remains at leastpartially impregnated within the fire retardant and heat resistantfabric.

The flurochemical further enhances the liquid- and gel-sheddingproperties of the fire retardant and heat resistant fabric beyond whatis provided by the silicone polymer encapsulation provided in Examples1-7. Enhancing the liquid- and gel-shedding properties of the fireretardant and heat resistant fabric further protects a wearer of thefabric from fire and heat if doused with a flammable liquid or gel, suchas gasoline.

Examples 15-33

Various treated fire retardant and heat resistant fabrics aremanufactured using any of the fabrics utilized in Examples 1-7. Thesilicone polymer coating used to treat the fire retardant and heatresistant fabric(s) according to Examples 15-33 are set forth in Table Ibelow. The amount of silicone resin in the polymer coating is in allcases 100-parts. The “mixture ratio” refers to the ratio of packagedcomponents as supplied by the manufacturer.

TABLE I Mix- Substituted Exam- Silicone ture Benzo- Other ple ResinRatio phenone Parts Additives Part 15 Silopren ® 1:1 Uvinul 400 5 71275/10 LSR 2530 Accelerator¹ 16 Silastic ® 1:1 Uvinul 400 5 Syl-off ® 50595 LSR 7611² 17 SLE 5100, 10:1  Uvinul 400 5 Sylox ® 2³ 8 Liquid BC-1:1 10 18 Silopren ® 1:1 Uvinul 400 5 Hydral ® 10 LSR 2530 710⁴ 19Silopren ® 1:1 Uvinul 400 5 Silopren ® 1 LSR 1530 LSR Z3042⁵ 20 SLE 550010:1  Uvinul 400 5 21 Silopren ® 1:1 Uvinul 400 5 2430 22 SLE 5300 10:1 Uvinul 400 5 23 SLE 5106 10:1  Uvinul 400 5 24 Silopren ® 1:1 Uvinul 4005 Flattening 4 LSR 2530 Agent OK412 ®⁶ 25 Silopren ® 1:1 Uvinul 400 5Nalco ® 50 LSR 2530 1SJ-612 Colloidal Silica⁷ 26 Silopren ® 1:1 Uvinul400 5 Nalco ® 50 LSR 2530 1SJ-612 Colloidal Alumina⁸ 27 Silastic ® 1:1Uvinul 400 5 200 Fluid⁹ 7 595 LSR 28 Silopren ® 1:1 Uvinul 400 5 LSR2530 29 Silastic ® 1:1 Uvinul 400 5 Zepel ® 3 595 LSR 7040¹⁰ 30Silastic ® 1:1 Uvinul 400 5 Zonyl ® 1/10 595 LSR UR¹¹ 31 Silastic ® 1:1Uvinul 400 5 Zonyl ® 1/10 595 LSR FSN-100¹² 32 Silopren ® 1:1 Uvinul 4005 DLX- 5 LSR 2530 600 ®¹³ 33 Silopren ® 1:1 Uvinul 400 5 TE- 5 LSR 25303608 ®¹⁴ ¹7127 Accelerator (Dow Corning) is a polysiloxane ²Syl-off ®(Dow Corning) is a cross-linker ³Sylox ® 2 (W. R. Grace & Co.) is asynthetic amorphous silica ⁴Hydral ® 710 (Alcoa) is a hydrated aluminumoxide ⁵Silopren ® LSR Z3042 (Mobay) is a silicone primer (bonding agent)mixture ⁶Flattening Agent OK412 ® (Degussa Corp.) is a wax coatedsilicon dioxide ⁷Nalco ® 1SJ-612 Colloidal Silica (Nalco Chemical Co.)is an aqueous solution of silica and alumina ⁸Nalco ® 1SJ-612 ColloidalAlumina (Nalco Chemical Co.) is an aqueous colloidal alumina dispersion⁹200 Fluid (Dow Corning) is a 100 cps viscosity dimethylpolysiloxane¹⁰Zepel ® 7040 (DuPont) is a nonionic fluoropolymer ¹¹Zonyl ® UR(DuPont) is an anionic fluorosurfactant ¹²Zonyl ® FSN-100 (DuPont) is anonionic fluorosurfactant ¹³DLX-600 ® (DuPont) is apolytetrafluoroethylene micropowder ¹⁴TE-3608 ® (DuPont) is apolytetrafluoroethylene micropowder

The silicone polymer resin and other components are mixed using aHockmayer F dispersion blade at low torque and high shear. The fireretardant and heat resistant fabric is tensioned and passed through abath containing the silicone resin composition. Localized high shear isapplied to the silicone resin composition near the surface of the fabricin order to coat the yarn strands comprising the fabric at a rate of 1.0oz/sq. yd. The fabric is passed through the polymer resin compositionseveral times to ensure thorough impregnation. After impregnation, theimpregnated fabric is removed from the silicone polymer composition bathand passed through a line oven of approximately 10 yards in length, as4-6 yards per minute, and cured at a temperature of 325-350° F.

Examples 34-60

Various treated fire retardant and heat resistant fabrics aremanufactured according to any of Examples 8-14. The fluorochemicalcompositions used to pretreat the fire retardant and heat resistantfabric(s) according to Examples 34-60 prior to application of thesilicone resin composition (which may comprise any of the compositionsof Examples 15-33 in Table I) are set forth in Table II below.

TABLE II Example Flurochemical 34 Milease ® F-14N 35 Milease ® F-34 36Milease ® F-31X 37 Milease ® F-53 38 Phobotex ® FC104 39 Phobotex ®FC461 40 Phobotex ® FC731 41 Phobotex ® FC208 42 Phobotex ® FC232 43Teflon ® G 44 Teflon ® NPA 45 Teflon ® SKF 46 Teflon ® UP 47 Teflon ®UPH 48 Teflon ® PPR 49 Teflon ® N 50 Teflon ® MLV 51 Zepel ® B 52Zepel ® D 53 Zepel ® K 54 Zepel ® RN 55 Zepel ® RC 56 Zepel ® OR 57Zepel ® HT 58 Zepel ® 6700 59 Zepel ® 7040 60 Scotchguard ®

Prior to applying the fluorochemical composition, the fire retardant andheat resistant fabric is washed with detergent, rinsed thoroughly, andhung to air dry. Thereafter, the fabric is soaked in water and thenwrung dry to retain 0.8 g water/g fabric. The fabric is then treatedwith a solution or suspension (e.g., a 2% solution) of thefluorochemical composition, taking into account the water already soakedinto the fabric (e.g., using a 2.5% solution of the fluorochemical). Thepretreated fabric is wrung through a wringer and air dried. The fabricis then heated in an oven for 1 minute at 350° F. to remove anyremaining solvent and sinter the fluorochemical. The fluorochemicaltreated fabric is then coated with a silicone polymer composition (e.g.,a composition from one of Example 15-33.

Example 61

Various treated liquid- and gel-shedding and strengthened fire retardantand heat resistant fabrics are manufactured using the fabrics disclosedin Examples 1-7, the silicone resin compositions of Examples 15-33, andthe fluorochemical compositions of Examples 34-60 (i.e., a wide range ofdifferent liquid- and gel-shedding and strengthened fire retardant andheat resistant fabrics are manufactured using every possible combinationof fabrics, silicone resin compositions, and fluorochemical compositionsof Examples 1-7, 15-33 and 34-60, respectively).

The fire retardant and heat resistant fabrics treated according to theforegoing examples have increased tensile strength, abrasion resistance,durability and liquid- and gel-shedding properties compared to thefabrics prior to treating with the silicone-based polymer. Because thesilicone-based polymer only encapsulates the individual yarn strands butnot the pores or spaces between the overlapping yarn strands, thetreated fabrics retain a level of breathability and porosity. Inaddition, the elastomeric properties of the silicone-based polymer allowthe fabrics to retain a level of flexibility and suppleness, which helpsmaintain the comfort of the fabrics if worn against a person's body.

The fabrics can be used in the manufacture of a wide variety of clothingand other articles where high fire retardance, heat resistance, andliquid and gel shedding capabilities are desirable. Examples include,but are not limited to, clothing, jump suits, gloves, socks, weldingbibs, fire blankets, padding, protective head gear, linings,undergarments, bedding, drapes, and the like. The treated fabrics andarticles are especially useful in the case where the wearer may becoated or doused with a flammable liquid or gel, such as a policemen orsoldier hit with a Molotov cocktail or other incendiary device.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A liquid-shedding fire retardant and heat resistant yarn, comprising:a fire retardant and heat resistant inner core comprised of: one or moretypes of fire retardant and heat resistant polymer fibers and/orfilaments having an LOI of at least about 50 and that do not burn whenexposed to heat or flame having a temperature of about 3000° F.; and oneor more types of strengthening fibers and/or filaments; and an outerliquid-shedding and strengthening shell encapsulating at least a portionof the inner core comprised of a liquid-resistant and strengtheningpolymer coating, wherein the liquid-shedding fire retardant and heatresistant yarn has increased strength, abrasion resistance, durabilityand liquid shedding ability compared to a yarn consisting exclusively ofthe fire retardant and heat resistant inner core.
 2. A liquid-sheddingfire retardant and heat resistant yarn as defined in claim 1, whereinthe fire retardant and heat resistant polymer fibers and/or filamentscomprise oxidized polyacrylonitrile.
 3. A liquid-shedding fire retardantand heat resistant yarn as defined in claim 1, wherein the fireretardant and heat resistant inner core includes oxidizedpolyacrylonitrile in an amount in a range of about 25% to about 99.9% byweight of the inner core.
 4. A liquid-shedding fire retardant and heatresistant yarn as defined in claim 1, wherein the fire retardant andheat resistant inner core includes oxidized polyacrylonitrile in anamount in a range of about 40% to about 95% by weight of the inner core.5. A liquid-shedding fire retardant and heat resistant yarn as definedin claim 1, wherein the fire retardant and heat resistant inner coreincludes oxidized polyacrylonitrile in an amount in a range of about 50%to about 90% by weight of the inner core.
 6. A liquid-shedding fireretardant and heat resistant yarn as defined in claim 1, wherein thestrengthening fibers and/or filaments comprise at least one of p-aramid,m-aramid, polybenzimidazole, polybenzoxazole,polyphenylene-2,6-benzobisoxazole, modacrilic, polyvinyl halide, wool,fire resistant polyester, nylon, rayon, cotton, or melamine.
 7. Aliquid-shedding fire retardant and heat resistant yarn as defined inclaim 1, wherein the inner core comprises at least one metallicstrengthening filament selected from steel, stainless steel, steelalloy, titanium, titanium alloy, aluminum, aluminum alloy, copper, orcopper alloy.
 8. A liquid-shedding fire retardant and heat resistantyarn as defined in claim 1, wherein the inner core further comprises atleast one ceramic strengthening filament selected from silicon carbide,graphite, or a high strength ceramic that includes at least one oxide ofAl, Zr, Ti, Si, Fe, Co, Ca, Nb, Pb, Mg, Sr, Cu, Bi, or Mn.
 9. Aliquid-shedding fire retardant and heat resistant yarn as defined inclaim 1, wherein the liquid-resistant and strengthening polymer coatingcomprises at least one type of cured silicone polymer resin.
 10. Aliquid-shedding fire retardant and heat resistant yarn as defined inclaim 1, further comprising at least one fluorochemical at leastpartially impregnated within the inner core that further imparts liquidshedding capability to the liquid-shedding fire retardant and heatresistant yarn.
 11. A liquid-shedding fire retardant and heat resistantyarn as defined in claim 1, wherein the yarn also has flammable gelshedding ability.
 12. A liquid shedding fire retardant and heatresistant fabric comprising: a plurality of liquid shedding fireretardant and heat resistant yarns (according to claim 1 that have beenwoven, knitted, or otherwise joined together into a fabric.
 13. A liquidshedding fire retardant and heat resistant article of manufacture formedfrom the liquid shedding fire retardant and heat resistant fabricaccording to claim
 11. 14. A liquid shedding fire retardant and heatresistant article of manufacture as defined in claim 12, wherein thearticle of manufacture is selected from the group consisting ofclothing, jump suit, glove, sock, welding bib, fire blanket, padding,protective head gear, lining, undergarment, bedding, and drape.
 15. Aliquid-shedding fire retardant and heat resistant yarn, comprising: afire retardant and heat resistant inner core comprised ofpolyacrylonitrile fibers and/or filaments; at least one fluorochemicalat least partially impregnated within the inner core; and an outerliquid-shedding and strengthening shell encapsulating at least a portionof the inner core comprised of a liquid-resistant and strengtheningsilicone polymer coating, wherein the liquid-shedding fire retardant andheat resistant yarn has increased strength, abrasion resistance,durability and liquid shedding ability compared to a yarn consistingexclusively of the fire retardant and heat resistant inner core.
 16. Aliquid shedding fire retardant and heat resistant yarn as defined inclaim 15, the fire retardant and heat resistant inner core furthercomprising one or more types of strengthening fibers and/or filamentsselected from the group consisting of p-aramid, m-aramid,polybenzimidazole, polybenzoxazole, polyphenylene-2,6-benzobisoxazole,modacrilic, polyvinyl halide, wool, fire resistant polyester, nylon,rayon, cotton, and melamine.
 17. A liquid-shedding fire retardant andheat resistant fabric, comprising: a plurality of liquid-shedding fireretardant and heat resistant yarn strands woven, knitted or otherwisejoined together to form the fabric, wherein the fire retardant and heatresistant yarn strands are comprised of polyacrylonitrile fibers and/orfilaments, wherein the fabric includes spaces between the yarn strands;and a liquid-shedding and strengthening shell encapsulating at least aportion of the yarn strands, wherein the liquid-shedding andstrengthening shell is comprised of a liquid-resistant and strengtheningpolymer coating that is applied so that the fabric maintains spacesbetween the yarn strands and remains porous and breathable, wherein theliquid-shedding fire retardant and heat resistant fabric has increasedstrength, abrasion resistance, durability and liquid shedding abilitycompared to a fabric consisting exclusively of the fire retardant andheat resistant yarn strands.
 18. A liquid shedding fire retardant andheat resistant fabric as defined in claim 17, the fire retardant andheat resistant yarn strands further comprising one or more types ofstrengthening fibers and/or filaments selected from the group consistingof p-aramid, m-aramid, polybenzimidazole, polybenzoxazole,polyphenylene-2,6-benzobisoxazole, modacrilic, polyvinyl halide, wool,fire resistant polyester, nylon, rayon, cotton, and melamine.
 19. Aliquid-shedding fire retardant and heat resistant fabric as defined inclaim 17, wherein the liquid-resistant and strengthening polymer coatingcomprises at least one type of cured silicone polymer resin.
 20. Aliquid-shedding fire retardant and heat resistant fabric as defined inclaim 17, further comprising at least one fluorochemical at leastpartially impregnated within the fire retardant and heat resistant yarnstrands that further imparts liquid shedding capability to theliquid-shedding fire retardant and heat resistant yarn strands.
 21. Aliquid shedding fire retardant and heat resistant fabric as defined inclaim 17, wherein the fabric forms at least part of an article ofmanufacture selected from the group consisting of clothing, jump suit,glove, sock, welding bib, fire blanket, padding, protective head gear,lining, undergarment, bedding, and drape.